Worktables with support devices that hold and direct various types of work pieces, such as wood, for cutting with saws and the like are known. These support devices may include guides such as fences, which can be used to safely direct cutting a work piece. Referring to FIGS. 1 and 2, a conventional sawing machine (i.e. miter saw) includes a base 1, a worktable 2 rotatably disposed on the base 1, and a cutting unit 3 which is coupled to the worktable 2. The base unit 1 comprises a base plate 101, two support legs 102 respectively mounted to two lateral sides of the base plate 101, two support frames 103 which are respectively mounted to the two support legs 102, two auxiliary fences 104 which are respectively disposed on outer lateral sides of the corresponding support frames 103, and two adjusting units 105 which are adapted for adjusting positions of the auxiliary fences 104 relative to the support frames 103. The adjusting units 105 are respectively engaged to the corresponding support frame 103 and the auxiliary fence 104. Each adjusting unit 105 includes two guiding slots 106 formed on the auxiliary fence 104 and two knobs 107 respectively extending through the corresponding guiding slot 106 which are adapted for fastening/unfastening the auxiliary fence 104 with the support frame 103.
When adjusting the position of the auxiliary fence 104 relative to the support frame 103, a user first loosens the two knobs 107 such that the auxiliary fence 104 is vertically slidable relative to the support frame 103; when the auxiliary fence 104 is adjusted to a desired position, the user respectively fastens the two knobs 107, such that the auxiliary fence 104 is securely positioned relative to the support frame 103 and is at an appropriate height relative to the worktable 2 for allowing cutting operation to be appropriately performed.
However, drawbacks of the conventional sawing machine are that, when adjusting the auxiliary fence 104, the user has to first use one hand to grasp the auxiliary fence 104, for allowing another hand to respectively loosen/fasten the knobs 107, which is inconvenient to operate and can also be time consuming. Additionally, because the knobs 107 have to be loosened/fastened respectively, the forces applied to the knobs 107 may be varied, such that the knobs 107 may be fastened with unequal forces. Furthermore, since the knobs 107 have to be respectively loosened/fastened, it is possible that the auxiliary fence 107 may be tilted horizontally upon adjustment due to adjusting the two knobs 107 individually. This prevents the cutting operation from being performed smoothly.